I found this video online with Microsoft engineer Blaise Aguera y Arcas (that's a mouthful) demonstrating the capabilities they're building into their Bing maps system.

I'd take a look at it, as it seems pretty damn cool; they're combining their Photosynth program with a Google Street View-like system, but with some key differences such as the ability to go indoors in some landmarks, 3D-viewing on the ground, and a really simple yet really cool astronomical viewing program.